Increased performance of circuit devices including transistors, diodes, resistors, capacitors, and other passive and active electronic devices formed on a semiconductor substrate is typically a major factor considered during design, manufacture, and operation of those devices. For example, during design and manufacture or forming of metal oxide semiconductor (MOS) transistor semiconductor devices, such as those used in a complementary metal oxide semiconductor (CMOS), it is often desired to increase movement of electrons in N-type MOS device (NMOS) and P-type MOS device (PMOS) contact regions. Such increased mobility can be achieved by reducing contact resistance.
At the contact regions of the source and drain a conductive material is deposited on the doped surface providing contacts. The interaction of the conductive material and the doped silicon substrate produce a silicide region. The resulting silicide region produces a Schottky barrier. Conduction of electrons through the Schottky barrier is limited by the barrier height and results in a contact resistance (Rcontact) as shown in FIG. 1. Accordingly, improved methods or structures are needed to overcome the limitations of conventional source/drain contacts.